(MONEY.CNN) — It is definitively a bad idea to visit pornography sites on your smartphone or tablet.

Nearly one-quarter of malware on mobile devices comes from porn websites, according to a new study from Blue Coat, a Web security and optimization company.

Mobile users don’t check out porn sites often — less than 1% of all mobile traffic is pornography. But when they do go to those sites, the risk of inadvertently downloading malware to their devices increases three-fold. That makes watching porn on smartphones a far bigger threat than viewing porn on a PC.

Porn led to more malware on smartphones and tablets than e-mail spam, malicious websites, and fake apps combined.